Heat large nonstick skillet over medium heat until hot.
Add ground beef; cook 8 to 10 minutes, breaking into 3/4-inch crumbles and stirring occasionally.
Pour off drippings. Stir in taco seasoning mix according to package directions; remove seasoned beef from skillet with slotted spoon.
Combine seasoned beef, tortilla chips, cheese and tomato in large bowl. Line 4 plates with salad greens. Top with beef mixture. Top with olives, onion and dressing, if desired.